Dielectric fitting assemblies are known in the art and have found use in many applications, ranging from natural gas pipelines, where they isolate monitoring instruments from the effects of electrical current and interrupt cathodic current flow while permitting fluid flow, to providing a conduit for transferring liquid through an aircraft bulkhead. In the latter usage, the dielectric fitting assembly includes fitting connections located on both sides of the aircraft bulkhead that permit connections of tubes, hoses, or other fluid-carrying components between them. Such a dielectric fitting assembly also provides a high electrical resistance path that limits electrical current flow between the two fitting connections but allows for the gradual dissipation of a precipitation-static (p-static) charge. If the fluid flowing through the dielectric fitting assembly has conductive properties that allow it to dissipate a static charge, the dielectric fitting assembly will need to provide only a very high electrical resistance approaching that of a non-conductor.
Thus, when used in an aircraft, a primary function of a dielectric fitting assembly is to dissipate the electrical energy from static charges caused in part by fluid movements and the indirect effects of lightning, at such an occurrence. These fitting assemblies have the equally important function of providing a safe fluid passage for the fluid passing through the fuel tank or other areas of the aircraft.
One such dielectric fitting assembly is disclosed in US-A-2008/0169643, which is incorporated herein in its entirety. This dielectric fitting assembly is shown in FIG. 7. The dielectric fitting assembly 200 of FIG. 7 includes a non-metallic hose 202 extending between two spaced apart metallic tubular end-fittings 204. The ends of the hose 202 are fastened to the end-fittings 204 by a metallic socket 206 that is crimped over the hose. The hose 202 has an electrically conductive inner layer that provides a specified electrical resistance and thereby, permits the dissipation of an electrostatic charge. The non-metallic hose 202 is described as being reinforced. A dielectric cover 208 surrounds the hose 202.